MATLAB 5.0 Enhancements (Upgrading from MATLAB 4 to MATLAB 5.0)

Upgrading from MATLAB 4 to MATLAB 5.0

New Data Constructs

MATLAB 5.0 added support for these new data constructs:

Multidimensional arrays
Cell arrays
Structures
Objects

In addition, MATLAB 5.0 featured character arrays that incorporate an improved storage method for string data.

Multidimensional Arrays

Arrays (other than sparse matrices) are no longer restricted to two dimensions. You can create and access arrays with two or more dimensions by:

Using MATLAB functions like zeros, ones, or rand
Using the new cat function
Using the repmat function
Indexing an existing array

MATLAB functions like zeros, ones, and rand were extended to accept more than two dimensions as arguments. To create a 3-by-4-by-5 array of ones, for example, use

A = ones(3,4,5)

The new cat function enables you to concatenate arrays along a specified dimension. For example, create two rectangular arrays A and B:

A = [1 2 3; 4 5 6];
B = [6 2 0; 9 1 3];

To concatenate these along the third dimension:

C = cat(3,A,B)

C(:,:,1) =

     1     2     3
     4     5     6


C(:,:,2) =

     6     2     0
     9     1     3

You can also create an array with two or more dimensions in which every element has the same value using the repmat function. repmat accepts the value with which to fill the array, followed by a vector of dimensions for the array. For example, to create a 2-by-2-by-3-by-3 array B where every element has the value pi:

B = repmat(pi,[2 2 3 3]);

You can also use repmat to replicate or "tile" arrays in a specified configuration.

**Table 1-1: New Multidimensional Array Functions**
Function	Description
`cat`	Concatenate arrays.
`flipdim`	Flip array along specified dimension.
`ndgrid`	Generate arrays for multidimensional functions and interpolation.
`ndims`	Return number of array dimensions.
`permute, ipermute`	Permute the dimensions of a multidimensional array.
`reshape`	Change size.
`shiftdim`	Shift dimensions.
`squeeze`	Remove singleton array dimensions.
`sub2ind, ind2sub`	Return single index from subscripts; subscripts from linear index.

Cell Arrays

Cell arrays have elements that are containers for any type of MATLAB data, including other cells. You can build cell arrays using:

The cell array constructor {}
Assignment statements (for instance, A{2,2} = 'string')

The new cell function

**Table 1-2: New Cell Array Functions**
Function	Description
`cell`	Create a cell array.
`cell2struct`	Convert cell array to structure array.
`celldisp`	Display top-level structure of a cell array.
`cellplot`	Graphically display the structure of a cell array.
`num2cell`	Convert a matrix into a cell array.

Structures

Structures are constructs that have named fields containing any kind of data. For example, one field might contain a text string representing a name (patient.name = 'Jane Doe'), another might contain a scalar representing a billing amount (patient.billing = 127.00), and a third might hold a matrix of medical test results. You can organize these structures into arrays of data.

Create structure arrays by using individual assignment statements or the new struct function.

Table 1-3: **New Structure Functions**
Function	Description
`fieldnames`	Return field names of structure array.
`getfield`	Get field of structure array.
`rmfield`	Remove structure fields.
`setfield`	Set field of structure array.
`struct`	Create structure array.
`struct2cell`	Convert structure to a cell array.

MATLAB Objects

Object-oriented programming is now available within the MATLAB environment.

Objects

The MATLAB programming language does not require the use of data types. For many applications, however, it is helpful to associate specific attributes with certain categories of data. To facilitate this, MATLAB allows you to work with objects. Objects are typed structures. A single class name identifies both the type of the structure and the name of the function that creates objects belonging to that class.

Objects differ from ordinary structures in two important ways:

Data hiding.. The structure fields of objects are not visible from the command line. Instead, you can access structure fields only from within a method, an M-file associated with the object class. Methods reside in class directories. Class directories have the same name as the class, but with a prepended @ symbol. For example, a class directory named @inline might contain methods for a class called inline.

Function and expression overloading. . You can create methods that override existing M-files. If an object calls a function, MATLAB first checks to see if there is a method of that name before calling a supplied M-file of that name. You can also provide methods that are called for MATLAB operators. For objects a and b, for instance, the expression a + b calls the method plus(a,b) if it exists

Table 1-4: New Object-Oriented Functions
Function
Description

class
Create or return class of object.

isa
True if object is a given class.

inferiorto
Inferior class relationship.

superiorto
Superior class relationship.

Character Arrays

Strings now take up less memory than they did in previous releases.
MATLAB 4 required 64 bits per character for string data. MATLAB 5.0 reduced the memory required to only 16 bits per character.

**Table 1-5: New Character String Functions**
Function	Description
`base2dec`	Convert base `B` to decimal number.
`bin2dec`	Convert binary to decimal number.
`char`	Convert numeric values to string.
`dec2base`	Convert decimal number to base.
`dec2bin`	Convert decimal to binary number.
`mat2str`	Convert a matrix into a string.
`strcat`	String concatenation.
`strmatch`	Find possible matches for a string.
`strncmp`	Compare the first `n` characters of two strings.
`strvcat`	Vertical concatenation of strings.

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Function	Description
`class`	Create or return class of object.
`isa`	True if object is a given class.
`inferiorto`	Inferior class relationship.
`superiorto`	Superior class relationship.